CAS is a gene that encodes a protein that is localized to microtubules and to the mitotic spindle. CAS is the mammalian homologue of CSE1, a yeast gene which controls mitosis. CAS may have a similar role in mammalian cells. Because CAS expression is high in proliferating cells, anti-CAS antibodies have been used as a proliferation marker in leukemia and lymphoma cells. Another interesting feature of CAS is that it is abundantly expressed in several nonproliferating tissues. We have identified different spliced forms of CAS mRNA which may confer different functions in these tissues. To help clarify the role of CAS, the mouse homologue has been isolated and has been used to construct knock out mice. The mice are now being characterized. - Apoptosis, cancer cell growth, Cell Cycle, cell proliferation, Oncogenes, regulation,